you should have the option to add an iCal feed by going to Settings -> Mail Settings -> Add Account -> Other Account -> Add Calendar Feed.
You can find the iCal feed in Todoist Preferences -> General Settings at the bottom of this window.
Thanks for your reply. However I have not been able to find Settings :( I did find Todoist Preferences, but have not find Settings. Where should I find it?
Thanks in advance and I am sorry
the Settings I was referring to should be accessible on your phone.